Setting up Java on macOS

Motivation

Setting up Java/ JAVA_HOME happens infrequently enough that I forgot how to do it efficiently, but frequent enough that it is annoying.

Problem?

I noticed MKYong’s method uses brew to install java JDK versions (recommended by OpenJDK) and then sets JAVA_HOME explicitly. He doesn’t use jenv because of “simplicity and no black box magic”. MKYong modifies JAVA_HOME to change the java version, and this will hide all other JAVA versions from being listed in /usr/libexec/java_home -V. Also, if that path is broken, no versions show up. I suggest not modifying JAVA_HOME, because in a few months when you want to switch your java version, java_home will still show you which versions you have on your machine.

jenv does 2 things

It allows switching between Java versions and sets JAVA_HOME for you. You can just read jenv’s Getting Started Guide now, but I’ve written the rest for my convenience, since I’ve set up too many machines this year (e.g. M1 Mac Mini, Intel i7 Hackintosh, MacBook Pro 16” from Popsa and my personal Intel MacBook Pro 13”).

Steps

  • Ensure Homebrew is installed

  • Run brew install --cask adoptopenjdk. Optional: read/ understand the AdoptOpenJDK homebrew tap

  • Add the tap so you can also install other versions of Java: brew tap AdoptOpenJDK/openjdk

  • Install the version of Java you want: brew install --cask adoptopenjdk11 or with any other version you want.

  • Warning: DO NOT modify JAVA_HOME yourself, because that is what jenv will do. If you’re updating an older system, get rid of your old code, e.g. export JAVA_HOME=... from your .bash_profile, .zprofile, .zshrc, or wherever you might have put it.

  • Install jenv: brew install jenv, and follow its output: it should say copy some lines into a configuration file.

  • mkdir -p ~/.jenv/versions, to prepare the folders for jenv to work properly. This is a workaround for a bug.

    • The bug: When trying to add a JAVA version to jenv using e.g. jenv add adoptopenjdk-16.jdk/Contents/Home, you’ll get ln: /Users/zen/.jenv/versions/openjdk64-16.0.1: No such file or directory.

  • jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-11.jdk/Contents/Home, remember to modify the path for your specific version. Notice the Contents/Home subdirectory.

  • Add more JDKs, for example for JDK15:jenv v

  • brew install --cask adoptopenjdk15

  • jenv add /Library/Java/JavaVirtualMachines/adoptopenjdk-15.jdk/Contents/Home/

  • jenv versions to list all JDKs

  • jenv global jdk_name to set a specific JDK, which also sets the JAVA_HOME variable for you. Check it with echo $JAVA_HOME. I prefer to run jenv global 15.

  1. java --version should show the version you just set:
openjdk 15.0.2 2021-01-19
OpenJDK Runtime Environment AdoptOpenJDK (build 15.0.2+7)
OpenJDK 64-Bit Server VM AdoptOpenJDK (build 15.0.2+7, mixed mode, sharing)

Conclusion

After finding jenv, I know I won’t be running into setting up Java anymore. I highly recommend it.